fix: endpoint /run api call could run same node twice (#3062)

fix: /run api call could run same node twice

src/backend/base/langflow/graph/graph/base.py

@@ -1046,7 +1046,8 @@ async def _execute_tasks(self, tasks: List[asyncio.Task], lock: asyncio.Lock) ->
         for v in vertices:
             next_runnable_vertices = await self.get_next_runnable_vertices(lock, vertex=v, cache=False)
             results.extend(next_runnable_vertices)
-        return results
+        no_duplicate_results = list(set(results))
+        return no_duplicate_results
 
     def topological_sort(self) -> List[Vertex]:
         """